Kafka Connect Sink is used to export data from Kafka to external databases and Kafka Connect Source is used to import from external databases into Kafka.

Consumers do not directly write to the __consumer_offsets topic, they instead interact with a broker that has been elected to manage that topic, which is the Group Coordinator broker

To reset offsets for anexisting consumer group, you must use thekafka-consumer-groups.shtool with the -- reset-offsets and --to-earliest flags.
FromKafka Consumer Group Tool Documentation:
"You can use the kafka-consumer-groups tool to reset offsets for a consumer group. This is required if the consumer has already committed offsets."
* Setting auto.offset.reset=earliest only worksif no committed offset exists.
* Starting a new consumer with the same group won't reset offsets.
* Retention settings don't affect committed offsets.
Reference:Kafka Consumer Group CLI Tool

Consumers can set auto.offset.reset property to earliest to start consuming from beginning. For KSQL, SET
'auto.offset.reset'='earliest';